US Patent 7697637 Demodulation circuit and demodulating method

A demodulation circuit can perform a capturing operation although a frequency error is large. A phase comparator out puts a predetermined value other than 0 as a determination result of a phase error when a phase error of a carrier wave is large and a signal point is located at a predetermined position. A loop filter outputs a negative minimum value to an integrator when an integrated value of a determination result reaches a positive maximum value of a limiter. Thus, when a phase error is large, a value changing from a negative minimum value to a positive maximum value is output from the loop filter, thereby realizing a broad synchronous capture range.